diff options
| -rw-r--r-- | kernel/exit.c | 57 |
1 files changed, 27 insertions, 30 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 81fcee45d630..877fae2cc705 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -439,6 +439,23 @@ static void coredump_task_exit(struct task_struct *tsk) } #ifdef CONFIG_MEMCG +/* drops tasklist_lock if succeeds */ +static bool try_to_set_owner(struct task_struct *tsk, struct mm_struct *mm) +{ + bool ret = false; + + task_lock(tsk); + if (likely(tsk->mm == mm)) { + /* tsk can't pass exit_mm/exec_mmap and exit */ + read_unlock(&tasklist_lock); + WRITE_ONCE(mm->owner, tsk); + lru_gen_migrate_mm(mm); + ret = true; + } + task_unlock(tsk); + return ret; +} + /* * A task is exiting. If it owned this mm, find a new owner for the mm. */ @@ -446,7 +463,6 @@ void mm_update_next_owner(struct mm_struct *mm) { struct task_struct *c, *g, *p = current; -retry: /* * If the exiting or execing task is not the owner, it's * someone else's problem. @@ -468,16 +484,16 @@ retry: * Search in the children */ list_for_each_entry(c, &p->children, sibling) { - if (c->mm == mm) - goto assign_new_owner; + if (c->mm == mm && try_to_set_owner(c, mm)) + goto ret; } /* * Search in the siblings */ list_for_each_entry(c, &p->real_parent->children, sibling) { - if (c->mm == mm) - goto assign_new_owner; + if (c->mm == mm && try_to_set_owner(c, mm)) + goto ret; } /* @@ -489,9 +505,11 @@ retry: if (g->flags & PF_KTHREAD) continue; for_each_thread(g, c) { - if (c->mm == mm) - goto assign_new_owner; - if (c->mm) + struct mm_struct *c_mm = READ_ONCE(c->mm); + if (c_mm == mm) { + if (try_to_set_owner(c, mm)) + goto ret; + } else if (c_mm) break; } } @@ -502,30 +520,9 @@ retry: * ptrace or page migration (get_task_mm()). Mark owner as NULL. */ WRITE_ONCE(mm->owner, NULL); + ret: return; -assign_new_owner: - BUG_ON(c == p); - get_task_struct(c); - /* - * The task_lock protects c->mm from changing. - * We always want mm->owner->mm == mm - */ - task_lock(c); - /* - * Delay read_unlock() till we have the task_lock() - * to ensure that c does not slip away underneath us - */ - read_unlock(&tasklist_lock); - if (c->mm != mm) { - task_unlock(c); - put_task_struct(c); - goto retry; - } - WRITE_ONCE(mm->owner, c); - lru_gen_migrate_mm(mm); - task_unlock(c); - put_task_struct(c); } #endif /* CONFIG_MEMCG */ |